Modulation of the near-infrared-I and -II luminescence of thulium-incorporated lead-free double perovskites

Currently, lanthanide-doped metal halide perovskites with near-infrared (NIR) luminescence are receiving considerable attention. However, they suffer from low NIR efficiency, particularly in the NIR-II emission range, and are primarily excited by high-energy ultraviolet light. In this work, high-performance NIR-I and -II emissions were realized by co-doping a Cs 2 NaInCl 6 lattice with Tm 3+ ions as luminescent emitters and Sb 3+ and Te 4+ ions as sensitizer ions, where Sb 3+ ions can enable short-wavelength high-energy excitation and Te 4+ ions can enable long-wavelength blue-light excitation. The NIR photoluminescence quantum yield (PLQY) reaches an unprecedented 58.0% in Cs 2 NaInCl 6 :Sb 3+ /Tm 3+ (NIR-II emission: 1224 nm-48.9%), which is attributed to the presence of the 1 G 4 energy level of the Tm 3+ ion acting as a bridge, efficiently transferring energy from high-energy states of Sb 3+ to NIR-emissive states. Moreover, Tm 3+ ions can be sensitized by Te 4+ ions that have broadband absorption in the blue region, which enable a high NIR PLQY of 10.3% in Cs 2 NaInCl 6 :Te 4+ /Tm 3+ under 420 nm excitation. The excellent NIR luminescence performance combined with excellent environmental stability endows Cs 2 NaInCl 6 :Sb 3+ /Tm 3+ and Cs 2 NaInCl 6 :Te 4+ /Tm 3+ with considerable potential for application in night-vision devices. High-performance NIR emission was observed in Cs 2 NaInCl 6 :Tm 3+ , where the sensitizer Sb 3+ achieved high-efficiency NIR emission and Te 4+ enabled blue-light excitation.